Sweden’s Alfa Laval and Norway’s OceanSaver confirmed they have both won type-approval from the US Coast Guard (USCG) for their ballast treatment system.

The approval comes after Norwegian peer Optimarin won the first type approval for a USCG-compliant ballast treatment system earlier this December.

Both companies submitted their application for type approval last September.

Alfa Laval’s system uses an ultra-violet light and mechanical filtration, while OceanSaver’s system uses electrochlorination and mechanical filtration. The first type of system is said to be more suitable for ships with slower ballast flow, while the second system is said to be more suitable for ships with fast ballast flow.

At least 10,000 ships have submitted waivers to the USCG for installing ballast treatment systems due to the lack of USCG-type approval.